Ecology and evolution news and commentary from Lincoln UniversityChristchurch, New Zealand

19 July 2010

Vegetarian zombie weevils rise from down under

A Canterbury Knobbled Weevil on Aciphylla.Photo by Mike Bowie, Lincoln University(used with permission).

In 2004, in an unsuspecting sleepy town in South Canterbury, zombies rose from the dead. Headlines were dedicated to spreading the news, zoologists world-wide were excited, all due to the rediscovery of a species thought to be extinct for 82 years! Wow, like the takahe? Well, maybe: a weevil. It may be smaller than the charismatic species we are used to hearing about, but no less important.

Despite the fact that specimens are located in history museums around the world, the endemic Canterbury knobbled weevil (Hadramphus tuberculatus) had not been seen alive for 82 years. To everyone’s great surprise, it was rediscovered in Burkes Pass in 2004 by Laura Young while she was studying for her Masters degree. It is currently one of New Zealand’s most endangered invertebrate species. The news at that time exclaimed how four specimens were found (and consequently pinned and archived). But what happened after that? Were there any survivors? Lincoln University researchers and students were quickly hot on the trail of this elusive large, flightless knobbled critter to find out.

Following the rediscovery, conservation efforts to save this species have been impressive, especially when we know so little about the species. Sampling measures have mainly included the use of pitfall traps and visual searches of the speargrass species that the weevil is known to primarily feed on (speargrass, or Spaniards, are species of Aciphylla, a famously spiky New Zealand plant in the carrot family). These efforts located more weevils within a second site on farmland across the road from the location of the initial rediscovery. However, until this last summer, all past efforts found very few additional weevils in either area. The summer of 2007–2008 recorded just six specimens; five located on Aciphylla, one in a pitfall, and the 2008–2009 summer returned no weevils at all. Thankfully, the past season (summer 2009–2010) found 49 weevils, the majority of which were recorded in the original area and all bar one were caught in pitfall traps.

Emily Fountain, a Lincoln PhD student currently studying the weevil, has hypothesised that the reasoning for these vast differences in weevil numbers between years is due to the ecology of the speargrass. Many threatened New Zealand birds put much more effort into breeding during the years their food plants flower heavily (“mast-seeding”). In contrast, Emily thinks that knobbled weevils are easiest to catch in years of poor flowering. Last summer very few plants flowered. Emily proposes that this caused a weevil mass movement, interplant dispersal, to locate more food resources that resulted in a very successful pitfall trap count. The previous two summers were good flowering years so the weevils are thought to not have needed to move around so much. This may be why the few specimens that were found were mainly located on the speargrass plants rather than between them.

Environment Canterbury and Department of Conservation staff in Twizel have both been frantically trying to protect the weevil and its habitat with the use of rat, stoat and hedgehog predator control since its rediscovery in 2004. Lupin spraying and the decapitation of wilding pine seedlings has also been a priority to stop competition with speargrass. The future conservation efforts for this species may include translocations, but this will only be once Emily’s research into the genetic health of the current population is completed. This research will allow us to see if the species is genetically stable enough to survive in additional populations. Until this time, a booklet has been released by Mike Bowie (Lincoln University) to inform farmers, and the general public, on what they can do to help locate more weevils and how they can aid in the species conservation. If you find a large knobbled weevil on a speargrass in Canterbury or Otago, please contact Mike.

Although the Canterbury knobbled weevil is, well, a weevil, its rediscovery was a significant event in New Zealand’s history. It reignited the awareness in the general public about the importance of the lesser known species. It also provides hope for other ‘extinct’ species that may be out there somewhere, still managing to survive under the radar of human detection, waiting for their chance to walk, or crawl, among the living again.

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Ecology & Evolution @ Lincoln

ecoLincNZ is written by the staff and students of Lincoln University. Research in ecology, evolution, conservation, and environmental management is spread across several departments and institutions on campus, including the Department of Ecology, the Bio-Protection Research Centre, and the Environment, Society, and Design Faculty. We specialise in research and teaching in the likes of entomology, plant pathology & crop protection, ecology, conservation & wildlife management, evolution, molecular genetics and biodiversity. We offer Bachelor of Science (B.Sc.) undergraduate degrees majoring in Conservation & Ecology and Bioprotection & Biosecurity, as well as a Bachelors in Environmental Management and Planning, and have a keen team of research staff, postdocs, and postgraduate students (M.Sc. and Ph.D.)

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